The basic idea behind the code is: Foo->bar(@_) is really a nice way of saying Foo::bar("Foo", @_) and $f->bar(@_) is Foo::bar($f, @_). After that, ref $self returns false for the string "Foo" (as it is not a reference) but the class name for the object.

I don't think it's a bad approach at all, but it will break existing subroutine-using code unless you somehow sniff what type the first argument is.

Since your functional interface already requires passing a reference on every call, I don't actually see why anyone would prefer to use it. Personally, if your module is not in too wide use yet, I would choose to retire it and tell the people depending on your module to change their code.

When putting a smiley right before a closing parenthesis, do you:

Use two parentheses: (Like this: :) )
Use one parenthesis: (Like this: :)
Reverse direction of the smiley: (Like this: (: )
Use angle/square brackets instead of parentheses
Use C-style commenting to set the smiley off from the closing parenthesis
Make the smiley a dunce: (:>
I disapprove of emoticons
Other